The production of a spun yarn takes place on spinning machines comprising a plurality of work stations arranged in several substantially parallel rows. During the operation of the machine, it is impossible to rule out the possibility that a smaller or greater yarn portion containing defects is spun out. If these defects are visible, or if they negatively affect the mechanical properties of yarn, which are essential in the process of further application of yarn, it is necessary to ensure that the defective yarn portion will not get onto the final wound bobbin of the spun yarn. It is therefore necessary to cut out the faulty yarn portion and join the remaining ends of the high-quality yarn. Such joints represent a local change in yarn diameter, which entails making a compromise so that the new joint will not represent an even greater fault in the yarn than the fault detected by the sensor.
The operation of a modern open-end spinning machine or the steps carried out by the operator to meet the requirements for yarn quality are known. A spinning machine is at each work station provided with a sensor of yarn quality, the so-called yarn clearer, which monitors the running spun yarn, including its diameter and its changes, changes of the colour or structure of the yarn, etc. Current sensors of yarn quality are due to high sensitivity able to respond even to minor changes which, however, may occur even on yarn portions of a greater length which have to be removed.
If a yarn change is detected at a work station of the machine, which is a signal of a possible defect, the process of recording the yarn length is automatically started. If after a certain predetermined period of time the criterion for cleaning the yarn is not exceeded, recording the yarn length is terminated without further intervention. On the other hand, if within this period of time the criterion for cleaning the yarn is exceeded, spinning is automatically terminated at this work station and the total length of the yarn spun between the time of detecting a possible defect and the time when the spinning operation is terminated is determined.
A suction nozzle of a work station is connected to a vacuum system of an open-end spinning machine, whereupon the entire length of the faulty yarn is unwound from the final bobbin, sucked into the vacuum system of the open-end spinning machine, and deposited in a respective space allotted for waste, whereupon the operator finishes the preparation of yarn for a new spinning-in operation.
The vacuum system of the open-end spinning machine is used to suck in the yarn ends after cutting out the faulty yarn portion or after a yarn breakage, to unwind this portion of the already spun yarn from the final bobbin and to suck it off, or to join the ends of the high-quality yarn by a pneumatic splicer.
Taking into account a great plurality of work stations of an open-end spinning machine, the high requirements for uniformity of the spun yarn, and the frequent use of the vacuum system for suction of a relatively great length of the faulty yarn, there is a high probability of the necessity of sucking off the faulty yarn simultaneously from numerous work stations. Solving this problem by increasing the rated power input of the vacuum source is, for such high numbers of work stations of an open-end spinning machine, uneconomical.
This drawback is not solved by the background art, or it is addressed by uneconomical means. The aim of the invention is therefore to overcome this drawback without increasing the performance of the vacuum source.